Abstract: A scan using an NMR imaging system is carried out while applying an oscillating stress to generate shear waves in the object being imaged. An alternating magnetic field gradient synchronized with the applied stress is employed in the NMR imaging pulse sequence to produce phase dispersion in the acquired NMR signals caused by the shear waves. The brightness of a reconstructed modulus image is thus modulated by the shear waves and this reveals mechanical properties of the object, such as stiffness.

Abstract: A scan using an NMR imaging system is carried out while applying an oscillating stress to the object being imaged. An alternating magnetic field gradient synchronized with the applied stress is employed in the NMR imaging pulse sequence to detect and measure synchronous spin motion throughout the field of view. The direction of the alternating gradient and/or the applied stress may be changed to measure and image the elastic properties of the object.

Abstract: An NMR image data set is acquired along with interleaved navigator signals. The navigator signals are acquired while two, orthogonal readout gradients are applied such that a circular orbit in k-space is sampled. The navigator signals are analyzed to detect object motion and to produce corrective values for the NMR image data to reduce artifacts caused by object rotation and displacement along two axes.

Abstract: In an NMR system a respiration monitor provides a visual feedback to the patient which enables the patient to perform a series of breath-holds with the patient's diaphragm positioned at the same reference point. This enables NMR data to be acquired over a series of breath-holds without introducing blurring or image artifacts. Between breath-holds a navigator pulse sequence is used to gather NMR data from which diaphragm position is measured, and during each breath-hold the pulse sequence is changed to gather NMR image data.

Abstract: An NMR echo signal is produced in a recursive process in which one or more pulse sequences are executed and the NMR echo signal produced by each pulse sequence is employed to shape the RF excitation pulse employed in the subsequent pulse sequence. The series of NMR echo signals produced by this recursive process are progressively modified to enhance the signals produced by prominent features in the subject.

Abstract: Motion artifacts are selectively suppressed in an image by correcting only the NMR data in the central views. The peripheral views are not corrected with the result that motion artifacts produced by large objects in the image are suppressed while motion artifacts produced by small objects are not. Consequently, the interior of small blood vessels remain darker in the reconstructed image.

Abstract: An NMR data set which is acquired with applied phase encoding and read-out gradients is corrected to reduce motion artifacts and increase image sharpness. The acquired NMR data set is examined to detect bulk displacements of the object being imaged and phase displacements caused by motion. This information is employed to produce correction operators which are applied to the NMR image data set. One or more navigator signals may also be acquired during the scan to produce an NMR data set from which the corrective operators can more readily be derived.

Abstract: A method for eliminating flow, motion and aliasing artifacts includes a series of saturation pulse sequences which are interleaved with the NMR pulse sequences used to acquire the data needed to reconstruct the desired image. Whereas, the NMR pulse sequences extract data from the volume of interest to be imaged, the saturation pulse sequences excite and saturate spins in the adjacent regions.